Thanks! I'll try this now. I emailed Eric Archer who's circuits started this thread. He thought the sound of my kick was ok. He had this to say about the 'click': there are lots of ways you can mod the kick to suit your taste. The click will be affected by certain capacitors. You can increase their value to roll off more of the click.

As yet, I haven't experimented with these values.

This is a sound clip of my kick. It starts with a pretty high decay setting and tone pot low, then I increase the tone and decrease the decay. I am triggering the kick using a 555 clock, a 4017 configured for 8 steps, using an AND gate made from a NAND IC (putting an inverted clock pulse to shorten it, plus the 4017 outputs into it to trigger consecutive steps from the 4017... if you know what I mean).

Well, after a long break, I'm back on this one. I finally got it wired up with the accent as suggested, but I'm getting exactly the same results as minus.

I'm now thinking there's maybe a fault in the translation over to stripboard (transistor pinouts, component misplacement etc), failing that, if there's a way to dampen the click noise, some form of resistor/capacitor filter somewhere, perhaps. Any suggestions?_________________My tunes available here
(check out the new Electro-Funk LP)

Further use and I no longer think the problem lies in the click being too loud, but more a problem with the sine being too quiet. The click should be there, and seems to cut through the mix as it should, the body (sinewave) of the kick on the other hand doesn't, and is way too low.

I'm now wondering if there's a resistor somewhere on one of the op amps restricting the output of the sine. Looking at the schematic, it appears IC1B takes care of amplifying this part of the circuit, now to find which resistor is restricting the level of the sine.._________________My tunes available here
(check out the new Electro-Funk LP)

Further use and I no longer think the problem lies in the click being too loud, but more a problem with the sine being too quiet. The click should be there, and seems to cut through the mix as it should, the body (sinewave) of the kick on the other hand doesn't, and is way too low.

I'm now wondering if there's a resistor somewhere on one of the op amps restricting the output of the sine. Looking at the schematic, it appears IC1B takes care of amplifying this part of the circuit, now to find which resistor is restricting the level of the sine..

my first post in this thread, but have you by any chance discovered a solution?

i'm pretty sure i'm in agreement with you about the click/sine balance, having listened to a bunch of original samples as well as clone samples. i'm quite curious to know if you've managed to find a way to 'tune' this...

I haven't got around to fiddling with this yet. Interesting to see LektroiD has had the same result. I don't have the electro-know-how to pin point this. I might send Eric Archer another email and see if he has any other suggestions. I have listened to some 808's and clones and there is a click there, but not as evident as this... Maybe it's a cap value wrong somewhere? But don't let this thought influence any desoldering!

Does anyone experience the level of the sine to be way too low? Compared to my oscillators it's barely audible. Maybe this part of it should be hooked up to another op-amp somewhere (thus hiding the click more).

I think a filtering capacitor would just reduce the click, but not increase the gain of the sine, which is evidently the problem here (you'd just end up with the entire output being way too quiet)._________________My tunes available here
(check out the new Electro-Funk LP)

Any progress here LektroiD? I've just plugged in my kick drum and the click is still there... surprise surprise. I'm thinking about opening the enclosure and desoldering some parts... I might change some cap values out of sheer desperation and see if I can find a solution to banishing this CLICK forever !

The other option as you pointed out, is to try increase the sine wave. This would mean a circuit add-on and a redo of the stripboard.

Looks like I'm going to go off on yet another huge tangent... followed by yet another disappointment .

I'll post results here....

EDIT: Just looking at the actual Roland schematic for this BD section, and comparing it to the redrawn schematic by Eric Archer... It all looks to be correct, with the exception of the trigger point add-on: a diode, followed by 100K resistor to ground, and the trigger signal going through a 0.1uF capacitor... I might first try altering these values.

OK... first test results. I have just bypassed the diode cap resistor add on and gone straight to the 22K resistor. This is R1 in Eric's schematic, and labeled as R152 according to Roland Corp . It is certainly making this less clicky, or more of the BOOOOOOM. I'll post a before and after sound clip soon...

What i might try is redo the diode, resistor to ground, and cap part at the trigger input. I really have limited electrical knowhow here, but I'm thinking a passive lowpass filter with the trigger signal going through the diode, through a resistor then a cap to ground.....? Worth a try, and nothing on my board has had to be desoldered.... YET!

I have some results to post. One clip is a comparison between triggering through the diode resistor cap set up as on the schematic of Eric's, and then running the trigger directly to the 22K resistor. For each test I have turned the decay pot roughly 45 degrees clockwise every time it runs through the pattern... I think going direct to the resistor as those men in white lab coats at Roland did, is the better of the two options. The decay has a much better range and overall I think the sound is less clicky and a lot fatter!

The other recording I'm posting is of the kick drum trigger wired direct to the resistor (as in the second half of the previous recording). decay is about half way... 12 o clock, and tone at about 10 o clock. I think it sounds ok in this example...

I am also posting two other links to MP3s. One is of a sound test of a kick drum from the MB808 (a TR808 clone). Notice the click! The other is from a real 808... it does have a click too. See what you think...

ah thanks for the reply! OK, so this seems to be more to do with the voltage than anything else. Looks like I need to sort out this bipolar power supply problem which I am frequently coming up against again and again. I might look around and see what options there are available... or post elsewhere on E-M and see what suggestions others have to make.

ah thanks for the reply! OK, so this seems to be more to do with the voltage than anything else. Looks like I need to sort out this bipolar power supply problem which I am frequently coming up against again and again. I might look around and see what options there are available... or post elsewhere on E-M and see what suggestions others have to make.

I was just looking at the stripboard for this bass drum in order to try figure out why my snare isn't triggering properly....

Anyway, I think the output on the stripboard is meant to go one strip lower. R25 would be redundant with the output in its present location. Not that it would matter a great deal, mind you. Just thought I'd mention it for future builders.

The more I look at these 808 schematics, the more I see similarities in the layout of each voice. I'm hoping that Slackers 808 kick stripboard may help me figure out where I am going wrong on the snare. The ACCENT and TRIGGER circuitry are identical in both...

I was just looking at the stripboard for this bass drum in order to try figure out why my snare isn't triggering properly....

Anyway, I think the output on the stripboard is meant to go one strip lower. R25 would be redundant with the output in its present location. Not that it would matter a great deal, mind you. Just thought I'd mention it for future builders.

The more I look at these 808 schematics, the more I see similarities in the layout of each voice. I'm hoping that Slackers 808 kick stripboard may help me figure out where I am going wrong on the snare. The ACCENT and TRIGGER circuitry are identical in both...

Thanks! I'm going to start building the kick on a stripboard this weekend. It will be my first project

Here is the image from the original pdf, but with the name next to the parts.
I had to make this because I've problems identifying the different parts in the german online shop (reichelt.de) since I'm pretty new to the field of electronics and don't know for example the difference between different capacitor types.

If anyone is still interested, I had a mess arround with the circuit and came up with these mods. They add a pitch control and changing C5 to a 22nf greatly increases the decay. With these mods, I found using a TL062 calmed things down a bit and made it sound spot on.

Pitch pot is 470k. Trigger from junction of R7 and C5.

I am not sure of the 'correctness' of any of these mods but it sounds very much like a TR808 to me!

You can use the more commonly available BC546 and BC 556 transistors instead - that's what Eric Archer uses too.

Re. triggering:
I seem to run into the same problems as some other folks here.

The normal trigger input doesn't work, and neither does Erics version with the added D3, R27 and C14 for "CMOS triggering".

It was mentioned here that one must apply a positive voltage of at least 3V to the "ACCENT" input in order to get the triggering to work.

Yup - this works now.
However, when I feed this circuit a pulse, I get the following:
An 808 impulse one octave higher than the normal pitch at the "high" state of the pulse
An 808 impulse at the regular pitch at the "low" state of the pulse.

What seems to work though is feeding the trigger input a very(!) short impulse, in other words an extremely short "high" state.

So is it normal that this circuit needs extremely short impulses to trigger correctly?

I shall note that I'm a bit of a n00b when it gets to trigger vs. gates and all this stuff

I've piggy backed a standard red LED onto the diode going to pin 3. I'm triggering at pin 3 too. What it's done is lost the accent pot use altogether, but it's cut that click volume down heaps!

Some of you might want to hook up a trigger signal to pin 3 and hold a LED on top of the diode and see what you think... it's probably dodgy electrical engineering practice and not even good circuit bending, but I can just about live with it this way.

On a slightly different note, I've been super impressed with Ken Stone's CGS-18 Drum Simulator. A very simple circuit with two drum voices and it sounds rather good!

EDIT: Still playing around with this. At the moment Im triggering at pin 3. I'm taking a wire from the trigger input through a pot (5k, that's what I had handy), through a 10uF cap to GROUND. This appears to give me control over the impact CLICK, without losing any of the BOOOOOOM.

hey hey! so the printed circuit board i picked up from radio-shack for $4 here in florida has a lay out of 55 x 40 ... i was wondering if it was possible to shorten some wire traces to fit TWO of these same circuits onto the 1 board, it would help much since i want to double this kick, along with the snare, hats, and clap (if i can find it) then stick those 8 into a case along with an Arduino Beat707 shield for cv from these voices and midi capability from other 80s drum machines... thanks for any responses! ._________________use your favorite search engine to find more from - Wizards of Zen

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